In a computer system, an operating voltage of a processor needs to be adjusted to accommodate different operating mode. The processor comprises Central Processing Unit (CPU) and Graphic Processing Unit (GPU) for example. Generally, a voltage regulator is employed to adjust the operating voltage based on a voltage identification (VID) code from the processor.
The voltage regulator provides a reference signal based on the voltage identification code, and the voltage regulator converts an input voltage to an output voltage based on the reference signal. The output voltage is used as the operating voltage of the processor. The voltage identification code may have a pulse width modulation signal compatible with an NVIDIA processor. However, traditional method to obtain the reference signal from the pulse width modulation signal has a large ripple and jitter, which would increase power loss.